Commit de synchro, see details

- Made a gem with the code
    * use require_relative in lieue of require
    * change file tree to match gems conventions
- Refactoring of HTTP
    * Direct/Proxy/Tor are now classes (simpler testing + inclusion)
    * Injected via httpstrategy in the scrapper initlization
    * All must respect a common interface (still need tests)
- Refactoring of Logger
    * Try to avoid the use of method_missing? (WIP)
    * Use #with(opt) to givea child logger (WIP)
- Refactoring of CentralStorage
    * retrieve, not retreive
- Scheduler:
    * Expose the #flush method, that... flush the job queue
    * Thread pool of one thread if debug env
    * Need better tests
- Rakelette:
    * no longuer destroy existing tasks
    * dynamic population of predefined producers OK
    * tasks are given an instance of the class and no longuer the class itself
    * still need produce:all + export:class
- Raclettte::Base
    * changes reflect the others refactorings